There exists a need in many industries to reduce large pieces of solid material to a particulate form. For instance, in managing wood and tree waste, it is desirable to grind stumps, branches, and wood scraps into smaller wood chips. Wood chips are more easily and efficiently transported, stored, and used for a variety of purposes. In other instances, it is desirable to reduce large pieces of waste material, such as plastic, for recycling or disposal.
Refiners of various size and operation are generally available for performing this function. One style of refiner includes a refining chamber defined by a sidewall and a bottom floor at one end of the sidewall. An annular ring in the same plane and surrounding the bottom floor is attached to the sidewall and rotates with the sidewall. For instance, reissue U.S. Pat. No. Re. 36,486 and U.S. Pat. No. 5,927,624, assigned to the assignee of the present invention, disclose a comminuter, or refiner, of this style. Inside the comminuter chamber, a rotatably-mounted toothed disk impacts solid material introduced into the chamber and reduces the material to particulate form.
The comminuter, or refiner, disclosed in the above-noted patents operates by rotating both the chamber sidewall and the toothed disk, usually in opposite directions. The rotation of the sidewall imparts rotational motion to the solid material placed in the chamber. As the material in the chamber rotates with the chamber sidewall, the material comes into contact with the rotating toothed disk. The teeth on the disk impact the material and thereby rip and tear the material into successively smaller pieces. The annular portion of the bottom of the chamber that rotates with the sidewall typically includes a screened exit through which the material, once refined to a particular size, may pass out of the chamber.
During the refining process, the solid material being refined may be thrown about within the comminuting chamber, particularly when the comminuting chamber is only partially filed. Portions of the material may ricochet off the rotating sidewall and fly out of the open top end of the comminuting chamber. To address this problem, reissue U.S. Pat. Re. 36,486 and U.S. Pat. No. 5,927,624 describe a curtain assembly mounted on top of a hopper stationed above the comminuting chamber. However, the curtain assembly can be complicated to assemble and partially blocks the opening of the hopper, adding some difficulty to loading material into the comminuter. Solid shrouding has also been suggested but that also partially blocks the opening of the hopper and/or comminuting chamber.
Screened exits in the comminuting chamber regulate the size of material that can exit the chamber. U.S. Pat. No. 5,927,624 describes an annular screened exit comprised of a series of grate segments. The grate segments have a plurality of holes, the size of which determine the particle size that can exit the chamber. When the operator desires to change the size of the particulate matter exiting the chamber, the comminuter must be stopped and unloaded, the grate segments removed and replaced with other grate segments having holes of a different size or configuration. Significant downtime of the machine thus occurs every time a change of particulate size is desired.
There is, therefore, a need in the prior art for a refiner with a refining chamber that better confines the material placed in the chamber to prevent it from inadvertently being thrown out. There is also a need for a refiner that is capable of changing the size of particulate matter exiting the refiner in a manner that is faster and easier than hitherto known. These needs, and other shortcomings in the prior art, are addressed by the present invention discussed herein.